1. Field of the Invention
The present invention concerns adhesively bonded, nonwoven webs having a majority of papermaking fibers and pre-moistened wipers comprising the web, a three component mixed polymer adhesive for the fibers of the web and a water base lotion containing borate ions for pre-moistening the web. .alpha.-hydroxy acids, o-aromatic hydroxy acids and keto acids are included in the lotion in one embodiment of the invention to achieve a synergistic effect.
2. Description of the Prior Art
Flushable non-woven webs and fibrous batts have been made having temporary wet strength. Two basic approaches have been taken to obtain temporary wet strength. One approach employs a polyvinyl alcohol gelled with borate ions which gel breaks down in the presence of a large volume of water but retains strength temporarily in the presence of limited quantities of liquid, see for example U.S. Pat. Nos. 3,645,928; 3,692,725 and 3,808,165 all issued to D. Duchane. A second method to obtain temporary wet strength is to blend a water insensitive polymer with a water soluble material. The water insoluble material retards the effect of water and the water soluble material provides cites for the water to slowly break down the adhesive and cause the web to disintegrate, see for example U.S. Pat. No. 3,554,788 entitled WATER DISPERSIBLE NON-WOVEN FABRIC. Such prior art methods usually rely upon the presence of textile length fibers in the web to impart wet strength due to long fiber length which causes entangling and roping of the fibers. A multi-layer approach to obtaining a pre-moistened, flushable wiper is disclosed in U.S. Pat. No. 3,881,210 which has a water dispersible, thermoplastic reinforcing layer. Fiber adhesives that are attached by specific enzymes to obtain dispersibility is disclosed in U.S. Pat. No. 4,009,313.
The prior art methods of obtaining temporary wet strength for a web are deficient with respect to maintaining wet strength over prolonged periods of time, (e.g., months) while wet with a water based lotion and subjected to extreme environmental conditions that can be encountered during shipment of commercial products and still be dispersible after use. Prior art methods either lost their wet strength during prolonged contact with the water base lotion or lost their ability to disperse when immersed in large quantities of water after being exposed to elevated temperatures, e.g., 140.degree. F. Furthermore, those systems which relied only upon the interaction of polyvinyl alcohol and a borate ion in the lotion required high concentrations of borate ions which is objectionable for lotions designed for cleansing human skin.